Other Constants

OPENSSL_RAW_DATA (int)
If OPENSSL_RAW_DATA is set in the openssl_encrypt or openssl_decrypt, the returned data is returned as-is. When it is not specified, Base64 encoded data is returned to the caller.
OPENSSL_DONT_ZERO_PAD_KEY (int)
Prevents openssl_encrypt from padding keys that are shorter than the default key length.
OPENSSL_ZERO_PADDING (int)
By default encryption operations are padded using standard block padding and the padding is checked and removed when decrypting. If OPENSSL_ZERO_PADDING is set in the openssl_encrypt or openssl_decrypt options then no padding is performed, the total amount of data encrypted or decrypted must then be a multiple of the block size or an error will occur.
OPENSSL_ENCODING_SMIME (int)
Indicates that encoding is S/MIME.
OPENSSL_ENCODING_DER (int)
Indicates that encoding is DER.
OPENSSL_ENCODING_PEM (int)
Indicates that encoding is PEM.